"Ask adults from the industrialized world what number is halfway between 1 and 9, and most will say 5. But pose the same question to small children, or people living in some traditional societies, and they're likely to answer 3. Cognitive scientists theorize that that's because it's actually more natural for humans to think logarithmically than linearly." Fascinating. The human brain is such a magical machine.

The research is about teasing out the way the brain actually works. That's why they want people to answer intuitively without thinking much about it.

I still find it difficult to believe that people would actually answer 3. Maybe there are such people, but the article does not quote the related statistics from the paper, and the wording does not make me believe it even could. (Anyway, small children can't count).

Also, this simple question does not form a very strong basis for building a whole theory on (in all fairness, judging from the article, they have other arguments). I would be interested what people who answered 3 (if there ARE such people) would answer to other ranges, e.g. 1 and 50 (most likely 10, not 7), 1 and 16 or 1 and 100. I like to play with the thought that as the number gets bigger, the answers would converge to the arithmetic mean.